PLANT TISSUES Lesson Description In this lesson we:
Identify the different types of plant tissue Be able to relate the different structures with the different functions
Summary Plant Tissue
12 MARCH 2014
LOCATION Apical – tips of roots and shoots Lateral – sides of roots and stems Vascular cambium – between xylem and phloem of dicots Cork cambium – inside cork cells Outer covering of roots, stems and leaves
Forms bulk of roots, stems, leaves and flowers.
In upper layers of leaves and stems Palisade and spongy mesophyll of leaves
In epidermis of young stems
STRUCTURE Thin willed Large nucleus No intercellular spaces Regular shape
Stems and leaves Guard cells surrounding a stoma Regular shape Thin walled No chloroplasts No air spaces Covered with a cuticle Roots Regular shape No cuticle Outgrows – root hairs Irregularly shaped round, oval Thin-walled, large vacuole Large intercellular spaces Lack chloroplasts Parenchyma tissue with chloroplasts Thin-walled, irregularly shaped with intercellular spaces. Elongated upper layer – palisade layer Regular shape No intercellular spaces Corners of cells are thickened
FUNCTION Actively dividing – Mitosis Produce new cells for Growth in length and width Replace worn-out or damaged tissue Differentiate into different types of tissue Protect deeper-lying tissue Cuticle reduced loss of water vapour by transpiration Guard cells control opening and closing of stoma, control loss of water vapour and gas exchange. In roots help to absorb water from soil.
Packing tissue Stores food as starch or sugars Intercellular airspaces allow water and gases to pass through. Manufactures food y photosynthesis.
Give support and strength to aboveground parts
Fibres In epidermis or stems Cap around vascular bundles of dicot stems Sheath completely around vascular bundle of monocots Stone cells in shells of nuts and hard parts of fruits Within veins of leaves, vascular bundles of stems and stele of roots
Fibres Long with tapered ends Thick- walled Very small inner cavities Stone cells Small, oval, irregular cells Extremely thick walls with lumens almost completely blocked.
Give mechanical support to plant.
Vessels and tracheids transport water and mineral salts from roots to stems and leaves Give strength and support
Within veins of leaves, vascular bundles of stems and stele of roots
Vessels Cylindrical cells Cross walls perforated or absent No cell contents – dead cells Form continuous tubes from roots to leaves Thick walls (lignin) Lignin laid down to form patterns Tracheids Ends tapered Have perforated cross walls Fibres and parenchyma as described above. Sieve tubes Cylindrical cells Cross walls perforated to form sieve plates Thin-walled cells Contain strands of cytoplasm continuous with that of next cell Living cells Companion cells Lie next to sieve tubes Thin walled with well defined nucleus Cross wall present Fibres and parenchyma as described above.
Sieve tubes transport manufactures food from leaves to all parts of body Companion cells probably control the activities of sieve tubes.
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